Rotary air pumps are used with material spreading tank machines to supply the tanks with air under pressure and alternatively evacuate the air from the tank. Control valves are used with the pumps to control the flow of air to and from the tanks. The air pumps are provided with lubricating systems for the bearings of the pumps. The lubricating systems have storage containers that allow oil to flow through lines connected to the housings of the pumps to lubricate the bearings of the pumps. The rate of flow of the oil from the containers to the bearings is regulated by manually operated valve structures.